This invention relates to the production of coke in a non-recovery type coke oven, and more particularly to apparatus for maintaining a desired operating temperature within ignition chambers employed to incinerate the distillation products liberated during the coking process for the smokeless operation of the coke oven.
As is known, there are two major methods for the manufacture of metallurgical coke. The earliest of these methods is a non-recovery type process wherein air is admitted into the coking chamber in controlled amounts for the purpose of burning the volatile products liberated from the coal charge without consuming the coal during the destructive distillation process. In this way, the heat generated by burning the volatile products is used to continue the distillation process. The smoke and other unburned volatile products liberated during the coking process were discharged into the atmosphere in the past. Because these emissions are a source of environmental pollution, the non-recovery type coking process has been largely done away with.
A more recent method for producing coke is known as a by-product or a retort process wherein air is excluded from a coking chamber during the distillation process and all volatile products liberated during the process are recovered as gas and other coal by-product chemicals. It is, therefore, possible to carry out a retort process in an essentially smokeless manner. Part of the distillation gases recovered as by-products are burned to provide the necessary heat to continue the coking process and the remaining portion of the distillation gases is processed to recover heretofore valuable coal chemicals. In recent years, coke producers using the by-product process have had difficulty disposing of the recovered coal chemicals on a profitable basis, particularly since many of the same or equivalent chemicals are recovered incident to the refining of petroleum products. The cost of producing coke by the by-product method can no longer be offset by the sale of by-product chemicals.
The non-recovery type coke oven is sometimes referred to as a beehive coke oven. Such coke ovens were built adjacent each other to form a coke oven battery. Coke was pulled from alternative ovens on alternate days so that the heat from the side walls of a hot coke oven would ignite the coal in a newly-charged and adjacent oven. The cycle for the production of coke by each oven chamber was about 72 hours. The non-recovery type coking process has again become an important factor to the coking industry, particularly in light of the more favorable economics of the process. A non-recovery type coking process is less costly and coke ovens used to carry out the process can be economically built at remote coal mine locations from where the coke can be shipped at less cost to facilities using coke such as blast furnaces.
In my prior U.S. Pat. No. 3,912,597, there is disclosed a smokeless non-recovery type coke oven wherein the distillation gases liberated during a coking process are conducted from the space above a coal charge downwardly along passageways in the side walls forming the oven chamber into a sole heating flue from where the gases are fed by a passageway into a tandem arrangement of ignition chambers. These ignition chambers are employed to carry out complete combustion of the partially-burned distillation products. A stack discharges the burned gases from the ignition chambers into the atmosphere. During the actual operation of such a coke oven, it is necessary to periodically perform needed repairs to the oven brickwork. Therefore, one or more coke ovens must be taken out of operation and permitted to cool down to an ambient temperature. After maintenance and repairs to the brickwork have been completed, an unusually and unacceptable long period of time is required to generate sufficient quantities of heat when operating on the natural draft produced by the stack so that the coking process can be carried out at the desired temperature. Moreover, a charge of off-grade coal may occasionally and unknowingly be charged into the oven chambers. This causes the temperature to drop within the oven chamber and the ignition chambers with an attending acute problem of undesirable and even unacceptable emissions from the stack. Such emissions will continue until a sufficient quantity of heat is restored in the coke oven and ignition chambers to carry out the coking process at the desired elevated temperature. When this form of non-recovery type coking chamber is activated from an ambient temperature, a booster fan in the stack is used to provide the necessary additional draft to overcome a resistance to the flow of gases created by the checkerbricks in the ignition chambers. The coking chamber is operated on an increased draft until the temperature of the oven has risen sufficiently and then the coking process will proceed on natural draft alone.
I have also discovered that when a coking chamber is at an operating temperature of about 2500.degree. F., there develops a back-pressure to the natural draft which causes poor and inefficient secondary combustion of the distillation products in the sole flues and passageways within the walls of the coke oven chamber. This secondary combustion does not incinerate the distillation products but does represent a partial combustion thereof. This, however, effects the efficiency of the coking process and causes a fluctuation to the temperature in the ignition chambers used to incinerate the gases. The temperature within the ignition chambers must be maintained at a minimum of, for example, 1400.degree. F. to incinerate all gases reaching this point and before the gases pass to the stack.